General and abdominal obesity parameters and their combination in relation to mortality: a systematic review and meta-regression analysis

Epidemiological studies assessing general and abdominal obesity measures or their combination for mortality prediction have shown inconsistent results. We aimed to systematically review the associations of body mass index (BMI), waist-to-hip ratio (WHR), waist circumference (WC) and waist-to-height ratio (WHtR) with all-cause mortality in prospective cohort studies. In this systematic review, which includes a meta-regression analysis, we analysed the associations with all-cause mortality of BMI, WHR, WC and WHtR in prospective cohort studies available in Medline, Embase, the Cochrane Database of Systematic Reviews and Esbiobase from inception through 7 May 2010. A total of 18 studies met the inclusion criteria, comprising 689 465 participants and 48 421 deaths during 5-24 years of follow-up. The studies were heterogeneous, mainly due to differences in categorization of anthropometric parameters (AP) and different approaches to statistical analysis. Both general and abdominal obesity measures were significantly associated with mortality. In analyses using categorical variables, BMI and WC showed predominantly U- or J-shaped associations with mortality, whereas WHR and WHtR demonstrated positive relationships with mortality. All measures showed similar risk patterns for upper quantiles in comparison to reference quantiles. The parameters of general and abdominal obesity each remained significantly associated with mortality when adjusted for the other. This evidence suggests that abdominal obesity measures such as WC or WHR, show information independent to measures of general obesity and should be used in clinical practice, in addition to BMI, to assess obesity-related mortality in adults.